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Full text of "The Cambridge Natural History"

2                               LARGE   SIZE   OF   MAMMALIA                        CHAP,
as a biting organ. The term highest, however, includes increased
complexity as well as simplification, the two series of modifica-
tions being interwoven to form a more efficient orynniMu. It
cannot he doubted that the increased complexity of 11m brain of
mammals raises them in the scale, as dot's also the enmplcx and
delicately adjusted series of bouelc.ts which form the or^un for
the transmission of sound to the internal ear. Tin* separation of
the cavity containing the lungs, and the investment of the parti-
lion so formed with muscular fibres, renders the action of the
lungs more, effective; and there are other instances among the.
Mammalia of greater complexity of the various parts and organs
of the body when compared with lower forms, which help tu
justify the term "highest" generally applied to these creature*.
Complexity and finish of structure are, often accompanied by
large si#e \ and the Mammalia are, on the whole, larger than any
other Vertebrates, and also contain the most colossal species The
huge. Dinosaurs of the Mesozoie epoch, though among the largest
of animals, are exceeded by the "Whales ; and the latter group
includes the mightiest creature that exists or has ever existed,
the eighty-five-feet-long Sibbald's l\onjuai Confining ourselves
rigidly to facts, and avoiding all thoonsing on the possible
relation between complexity and nicety of build and the capacity
for increase, in bulk, it is plain from the history of more than
one group of mammals that inereasein bulk accompanies specialis-
ation of structure. The huge iJinueevuta when compared \uth
the ancestral Pnntohnnhthi tendh us this, IIH do many similar
examples Within the mammalian group, an in the, ease of other
Vertebrates, difference of mm haw a cerium rough wnvHpoiidene-e
with difference, of habitat The Whales not only contain the.
largest of animals, but their average, sixe in great; m too with
the equally aquatic Hirenta and very aquatic, Hnnipediit, Here
the support offered by the water and the consequent tlerrejiBinl
need for muscular power to neutralists the ettitctH of gravity
permit of an increase in bulk. Purely temtstnul uniiualn come
next; and finally arboreal, awl, ntill maw, " flying" luannnalH
are of small Bi^e, siiic-e the rnainttumnee of the poHitioii when
moving and feeding neecln eiionnoun nmwular oflort*
The Mammals are more uu#ily tci bo |iaratfHl from the*
Vertebrates lying lower in the Bevies thai* any of the latter are
from each other in uacoudiug order, A lurge number of char-